Control mechanism for radio apparatus



April 19, 1952. J. MENDOLA 1,854,555

CONTROL MECHANISM FOR RADIO APPARATUS Filed July 1'6, 1930 ATToRN Patented Apr. 19, 1932 Ufrug'rvrzila STATES PATENT OFFICE .JOSEPH MENDOLA, F ROCHESTER, NEW YORK CONTROL'MECHAN ISM FOR RADIO APPARATUS Application filed JulylG, 1930. Serial N0. 468,402.

Vsystem having adjustable means for limiting the eXtreme movement of the control mechanilsm for* preventing strain upony the belt driving system. n l t A further object 0f mylnvention 1s lto pro- -vide an attachment for a control mechanism and a belt driving system in which strain .on the belt Vmay be relieved by predetermining the position at which movement of the control is brought to a stop.

A still further obJect of my invention is to 4 provide an adj ustable stopmechanism adapted tobe applied to standard forms of instrument control for actuating a driving belt lwithin predetermined limits while preventing n undue strain upon: the belt. n

Other andr further objects of myinvention reside in the construction of protective device for insuring the eiiicient operation of thecontrol mechanism of an electrical tuning apparatus as set forth .more fully in the specification hereinafter following by'reference to the accompanying drawings, in which:

Figure l is a side elevation of an indicator drum and pulley showing the control means lof my invention associated therewith for the annular movement4 of the control shaft connected-with the indicator drum; Fig. 2 is a front elevation of `atuning condenser and control shaftv coupled .theretol with the attachment of my invention appliedthereto Fig.. 3

is aside elevation on an enlar ed scale of the .limitingy stop. arrangement o my invention applied to thecontrol shaft Fig. 4 is a cross- -sectional view taken throughthe parts of the afIllSl'Il.

limiting stop mechanism and control shaft with parts illustrated inside elevation; Fig.

5 isa fragmentary view taken partially in cross-section on line 5-5 of Fig. 2l; Fig. 6 is a cross-sectional View taken on line 6 6 of Fig. 4; Fig. 7 is a cross-sectional view taken through the position limiting device of my invention online 7 7 of F ig'. 4; and Fig. 8 is a perspective view illustrating thearrangement of the several parts of the position limiting device of my invention.`

My invention is particularly adaptable for radio receiver apparatusfin relieving undue strain on the driving cord or belt in an adjustable tuning mechanism. Heretofore iny constructions of tuning control mechanism employing a driving belt difficulty has been experienced due to slaclness occurring in the drive belt resulting` in slippage of the control and impairing the operationof the receiver. In the operation of a radio broadcast Y receiver in the home itis not unusual for the tuning control to receive considerable mistreatment. That is, the tuningV control may be carelessly rotated back and forth and torsional stress applied to twist the tuning control beyond the normal stop so often'that the drive cord is stretched or broken and thereafter tends to jump away from the pulley and no longer functions to. impart accurate movement to the shaft of the tuningapparatus.

:As a resultV of undue stretching the cord or Vbelt merely slips around the drive pulley and it is no longer possible to control the tuning apparatus. Y y

vBy my invention I provide means for predetermining the position oflimiting stops at each extreme in the arc of movement of the vcontrolshaft for preventing undue strain on the driving cord or belt and thereby accuratelypreserving the adjustment of the tuning mechanism. The. predetermining position stop mechanism of my invention maybe readily applied ,to standard forms of. belt drive inthe tuning controls of radio/,appa-v ratus. The construction of theA parts ofthe predetermining position mechanism is such 1 that they may be readily mounted with respect to the control shaft'ofthe tuning mech- Referring to the drawings in detail, reference character 1 indicates the adjustable shaft of a tuning apparatus such as a multiple unit gang condenser 3, including sets of stator and rotor plates indicated at 3a, 37), 3c, and 3d respectively. An indicator drum 2 is mounted on the indicator control shaft 1 and has pulleys l immediately adjacent thereto over which the drive cords 5 are looped. The drive cords 5 may be secured as indicated on the pulleys t as at 12 and secured at their extremities to the peripheral spirally grooved drums 14 and 15 grooved for the reception of drive cords. The drums 111 and 15 are rigidly carried by shaft 18. VEhe drum 14 is rigidly secured to shaft 8 Voy a set screw 11i@ which enters a preformed socket 8a in shaft 8. The drum 15 may be similarly secured to shaft 8 by means of set screw 150J which extends into the preformed socket 8b in shaft 8. The shaft 8 is ournaled in bearings provided in the upturned ends 16 of the yoke 10. The yoke 10 is mounted upon the base plate 11 of the condenser chassis by means of screw members indicated at 11a and 11?). The control shaft 8 is adapted to receive a sleeve member 17 exteriorly screw threaded throughout a portion of its length. The sleeve 17 is firmly secured to the shaft 8 by means of set screw 19 which extends into a preformed socket 8c in the control shaft 8 thereby rigidly maintaining the sleeve 17 in position on shaft 8 in such manner that the sleeve 17 rotates with the movement of control shaft 8 which is in turn controlled from externally extending shaft 9. A carriage 20 is internally screw threaded to receive the screw threads 18 of the sleeve 17 and is provided with a radially projecting pin 21 screw threaded therein which pin is adapted to move longitudinally in a slot 22 formed in the yoke 10. The slot 22 in the yoke 10 has such a length as is necessary to predetermine the limits of movement of the control shaft 8. The pin 21 abuts against the end of the'slot 22 in the course of the driving movement effected by rotation of the shaft 8 and screw threaded sleeve 17 attached thereto and engaging the interior screw threads in the carriage 20. This abutment provides a positive stop for the shaft 8 and prevents further pull on cord 5. The same limit of rotation may be obtained at the opposite limit of movement of the indicator drum by abutment of pin 21 against the opposite end of slot 22. It is understood that the movement of the indicator drum and associated tuning apparatus is substantially 180o so that the slot 22 is formed of such size that full movement of the indicator drum and associated tuning apparatus is obtained without introducing undue stress and strain upon the cord or belt 5. Where it is desired to reduce the path of travel of the carriage 20 I provide an adjustable member 23 in the form of a strip having an upturned edge 24 which may be advanced or retracted with respect to the path of movement of the carriage 20. The end of the adj ustable member 23 is bifurcated as indicated at 25 for the passage of a screw member 26 therethrough. The screw member 26 extends upwardly through plate 11 and yoke 10 and has an adjustable nut 27 thereon. The adjustable member 23 has a cylindrical aperture 23a therein in which the eccentric 28 is located. An adj usting screw 29 extends upwardly through plate 114 and yoke 10 into the eccentric 28 enabling adjustment of the eccentric to be made for the advancement or retraction of strip member 23 along yoke 10. By moving the upstanding end 24 of strip 23 into the path of carriage 20 the limit of rotation of control shaft 8 maybe further reduced thus preventing undue strain on the cord or belt 5.

The adjustable member 23 is necessary in predetermining the stop position of the control shaft 8 due to inaccuracies in manufacture and stretching of the cord or belt 5. Fromtime to time the strip member 23 may be adjusted to compensate for stretching-of the drive cords under operation or temperature influences. l

Due to the simplicity of the predetermining position stop device of my invention, the device of my invention may be readily applied to tuning mechanism of standard types. I have found that the device of my invention increases the ability of the tuning condenser to withstand shock movement brought about by excessforces applied in either a clockwise or counterclockwise direction upon the control knob. The accuracy of the apparatus may thus be maintained and the receiver tuning control rendered substantially safe even in the hands of an unskilled operator.

Vhile I have described my invention in certain preferred embodiments I desire that it be understood that modifications may be made and that no limitations upon my invention are intendedv other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. An electrical tuning apparatus comprising a rotatable instrument shaft, a pulley carried by said shaft, acontrol shaft extending normal to said rotatable instrument shaft, a drive cord looped over said pulley and operative by movement of said control shaft to impart angular 'movement to said rotatable instrument shaft,Y an externally screw threaded sleeve 'concentrically secured to said control "shaft, a longitudinally movable carriage shiftable along said externally screw threaded sleeve, a member projecting from said carriage in the path of predetermined position stops,and an adjustable stop adjacent one of the limiting stops for limiting the travel of said movable carriage in one direction, whereby the rotation of said instrument shaft beyond predetermined limits is prevented and strain upon said drive cord eliminated.

f2. In a control apparatus, a rotatable shaft, an externally screw threaded sleeve member carried by said shaft, a screw threaded carriage engaging said sleeve member, a pin on said carriage proj ectible into the ath of pre determined positioned stops, and) an adjustable stop adjacent one of the limits of travel of said carriage for preventing the movement of said carriage beyond a predetermined position while permitting the angular adjustment of said control shaft within predetermined limits.

3. A control apparatus comprising a frame structure, a rotatable control shaft j ournaled in said frame structure, an externally screw threaded sleeve on said control shaft, a screw threaded carriage engaging said externally screw threaded sleeve, a pin on saidcarriage projecting into a slot in said frame structure for predetermining the limits of travel of said carriage, and a member movable with respect to said frame structure into the path of said carriage for limiting the travelof said carriage and correspondingly predetermining the limits of rotation of said control shaft.

.30 l. A control apparatus comprising a frame structure, a rotatable control shaft journaled in said frame structure, an externally screwk threaded sleeve on said control shaft, a screw threaded carriage engaging said externally screw threaded sleeve, a pin on said carriage projecting into a slot in said frame structure for predetermining the limits of travel of said carriage, a member carried by said frame structure in alignment with said movable carriage and adjacent said slot, and an eccentric operative Vthrough said frame structure for advancing or retracting said member in the path of said carriage for adjustably defining the limit of travel thereof, whereby the rotation of said control shaft may be correspondingly limited. Y

In testimony whereof I aix my signature.

JOSEPH MENDOLA. 

